Nicotine enhances acquisition of a T-maze visual discrimination: assessment of individual differences

In the present report, rats' performance was assessed in five tasks designed to measure behavioral response to different novel stimuli under different experimental situations. Daily nicotine treatment (0, 0.3 or 1.0 mg/kg) began after the conclusion of the behavioral tasks and continued throughout the experiment. Training of a T-maze visual discrimination task commenced after 11 days of nicotine pretreatment. As a group, rats treated with the higher dose of nicotine (1.0 mg/kg) made fewer errors to acquire the initial T-maze discrimination than saline-treated controls. Activity induced by an inescapable novel environment (i.e. first behavioral screen) was positively correlated with the number of errors to acquire the initial discrimination in the T-maze for the two nicotine-treated groups (0.3 and 1.0 mg/kg). To examine this positive correlation further, a median split analysis was conducted on the novelty-induced activity for each group. Nicotine, especially the high dose (1.0 mg/kg), enhanced performance in rats that were less active in the inescapable novel environment. Nicotine treatment did not affect the performance of rats that were more active in that environment. After the initial visual discrimination was acquired, the reverse discrimination was trained. Nicotine treatment did not affect performance; the number of errors to acquire the reversal for nicotine- and saline-treated rats did not differ. Overall a nicotine-induced improvement in performance is demonstrated which can be predicted by a rat's reactivity to environmental novelty. (C) 2000 Lippincott Williams & Wilkins.